The volcanic soils of the Auckland isthmus create a complex permeability puzzle. Basalt flows, scoria cones, and tephra layers sit alongside alluvial sands and marine clays. Water movement through these materials varies dramatically over metres. A single borehole can intersect both free-draining pumice and near-impermeable claystone. That is why a field permeability test in Auckland must use the right method for each horizon. The Lefranc test works in low-permeability soils where steady-state flow is slow. The Lugeon test suits fractured rock masses like the Waitemata sandstone or East Coast Bays Formation. Without site-specific hydraulic data, excavation dewatering and foundation drainage designs rely on guesswork. Our team applies these methods across the Super City, from Britomart basements to motorway cut slopes.
Volcanic stratigraphy in Auckland can change permeability by three orders of magnitude within a single borehole. Stage testing is non-negotiable.
Methodology and scope
A common mistake contractors make in Auckland is assuming a single k-value applies to the entire site. The volcanic stratigraphy is too heterogeneous. We saw a development in Three Kings where one side of the site had k=10⁻⁴ m/s and the other k=10⁻⁷ m/s. The drainage design failed because it used an average value. Field permeability tests must be staged by depth and soil type. The Lefranc test maintains constant head in a cased borehole while measuring flow into the test section. For rock, the Lugeon test uses five pressure steps to identify laminar or turbulent flow. Results guide decisions on grouting programs for seepage cut-offs and dewatering system sizing. Our laboratory holds ISO 17025 accreditation for these procedures.
Technical reference image — Auckland
Local considerations
A 10-storey apartment block in Newmarket was being excavated into weathered East Coast Bays sandstone. The geotechnical report had estimated k=10⁻⁶ m/s based on grain size analysis. After heavy rainfall, the excavation walls began weeping across the entire face. A field permeability test in Auckland using the Lugeon method revealed a fracture zone with k=10⁻⁴ m/s. The dewatering system was undersized by a factor of five. Construction stopped for three weeks while additional pumps and a cut-off wall were installed. The delay cost over NZ$200,000. The lesson is clear: never rely on indirect permeability estimates for urban basement excavations in Auckland.
Lefranc (constant / falling head) or Lugeon (packer)
Typical k range
10⁻⁴ to 10⁻⁸ m/s (Lefranc); 10⁻⁵ to 10⁻¹¹ m/s (Lugeon)
Borehole diameter
NX (76 mm) or HQ (96 mm)
Test section length
1.0 m to 3.0 m (Lefranc); 3.0 m to 5.0 m (Lugeon)
Pressure stages (Lugeon)
5 ascending steps, 1 descending, 1 repeat
Water source
On-site tanker or mains supply (min. 500 L)
Associated technical services
01
Lefranc constant head test
For soils with k between 10⁻⁴ and 10⁻⁷ m/s. Uses a cased borehole and a Mariotte bottle to maintain constant water level. Suitable for alluvial sands and volcanic ash layers common in central Auckland.
02
Lefranc falling head test
For low-permeability soils (k below 10⁻⁷ m/s). Measures the rate of water level drop in a standpipe. Ideal for the stiff marine clays of the Waitemata Harbour shoreline.
03
Lugeon packer test
For rock masses and cemented soils. Uses an inflatable packer to isolate a test interval. Five pressure stages identify fracture flow and assess grout take. Applied to Waitemata sandstone and East Coast Bays Formation.
04
Constant head injection test
For highly permeable gravels and scoria. Injects water under constant pressure. Determines k for drainage layer design. Used in Auckland's volcanic cones and alluvial floodplains.
What is the difference between the Lefranc and Lugeon field permeability tests?
The Lefranc test is designed for soils and uses a cased borehole with a constant or falling water level. It measures hydraulic conductivity in the range 10⁻⁴ to 10⁻⁸ m/s. The Lugeon test is for rock and uses an inflatable packer to isolate a section, applying five pressure steps to distinguish laminar from turbulent flow through fractures. In Auckland, we use Lefranc for volcanic soils and Lugeon for weathered sandstone.
How much does a field permeability test in Auckland cost?
A standard field permeability test in Auckland typically ranges between NZ$960 and NZ$1,850 per test section. This includes mobilisation, one test method (Lefranc or Lugeon), equipment setup, and a written report with k-values and flow regime interpretation. Costs increase for remote locations, multiple packer intervals, or if a water tanker is required. Contact us for a site-specific quote.
Where in Auckland are field permeability tests most critical?
Field permeability tests are most critical in three zones: the volcanic cones (Mount Eden, Mount Roskill) where scoria layers create preferential flow paths; the Waitemata sandstone belt along the eastern suburbs where fractures control seepage; and the alluvial floodplains of the Manukau Harbour where sands can cause rapid dewatering failure. Any basement excavation or cut slope in these areas should include staged permeability testing.
